1. Field of the Invention
The present invention relates to an information storing method and an information storing system wherein information is written into and read out of a storage medium such as an optical disk. More particularly, it relates to an information storing method and an information storing system wherein data to be treated by a generalized operating system can be stored in and reproduced from a storage medium in a state which is ready to be treated by the operating system.
2. Description of the Prior Art
In recent years, optical disks have been developed as media for storing information, and they have been used for storing image information because of their large storage capacities. Most notably, a rewritable type of optical disk permits information to be rewritten like a conventional magnetic disk and is therefore utilized for the construction of a file system.
In this regard, since the optical disks have been chiefly employed for the storage of image information, writing and reading the image information into and from the storage medium normally employs dedicated processing programs. In case of storing code data, therefore, the code data needs to be first converted into image data, and then be stored. This method, however, poses the problem that the data retrieved cannot be directly utilized, and a process for converting the image data into code data is required.
On the other hand, a technique for storing image data and code data coexistingly on an optical disk is discussed in a treatise, "Izawa et al.: Toshiba Review, 1989, Vol. 44, No. 1, pp. 49-52". The technique includes generating on the optical disk an area having a hierarchical storage structure (data organization and format), and storing the code data in the lowermost layer of the hierarchic structure for storing the image data items. With this technique, information for distinguishing the image data and the code data is appended to each of those additional information (index information) items of the image data items which are held in 1:1 correspondence with these image data items. Thus, the code data left intact can be stored similarly to the image data.
The prior-art technique stores the code data within the storage structure for the image data. Accordingly, the code data can be accessed from an image processing program. The technique, however, has had the problem that, in a case where the code data is to be accessed from another program having different storage structure, such as a generalized operating system, it cannot be directly accessed. In this case, it has been necessary to access the code data through another storage medium, such as a floppy disk, having a storage structure which the other program can deal with. Conversely, in order to permit the image processing program to access the code data, this program must know the storage structure of the other program, which is burdensome.
Therefore, in an information storing system having dedicated processing programs for storing and reproducing image information, it is desired to develop a system wherein data to be treated by a generalized operating system can be stored on and reproduced from a storage medium in a state in which it can be directly treated by the operating system.
Meanwhile, as to the generalized operating system, for example, "MS-DOS" of Microsoft Inc., there is a technique wherein, in order to prevent the size of an available storage area from being limited by the size of the storage area of a physical memory, the area of the physical memory is segmented into a plurality of suitable sizes, and information is stored in each of the segmental areas which is logically regarded as one memory or one driver. In this case, the individual segmental areas of the storage area of the physical memory are uniquely endowed with logical driver identifiers. Data can be stored and reproduced in such a way that an operator designates the logical driver identifier without being conscious of the physical memory or the address of the area thereof. With this technique, the logical driver identifiers and the physical storage areas are held in 1:1 correspondence, and a the corresponding driver identifier is designated for each segmental storage area.
In the case where the storage medium is segmented into the plurality of areas endowed with the logical driver identifiers, respectively, the number of logical driver identifiers which can be bestowed is often finite. Besides, in order to simplify the bestowal of the logical driver identifiers, each logical driver identifier is defined using, for example, a single digit numeral or a letter of one character.
However, the number of the logical driver identifiers which can be bestowed might become deficient as the number of segmental areas increases with the enlargement of the physical storage capacity. By way of example, in a case where the physical memory itself has a very large storage capacity such as in an optical disk or where it is furnished with a large storage capacity as a whole by employing a large number of storage media, only part of the storage capacity is utilizable even with the maximum number of logical driver identifiers which can be bestowed.
In addition, in order to permit the information storing system to store and reproduce data into and from the storage area in the state in which the generalized operating system can handle, the pertinent storage area needs to be initialized to have a storage structure the operating system can deal with. Besides, in order to change the size of the segmental area after the storage area has been once initialized, this area needs to be initialized again. However, the initialization results in losing the stored data. Therefore, it is actually difficult to alter the size of the segmental area once it is set. It is accordingly considered to expand the segmental storage area associated with each logical driver identifier for the purpose of effectively using the physical storage capacity with the limited number of logical driver identifiers, but this measure is difficult to realize.
Incidentally, as to the storage of code data on an optical disk, there is a technique wherein the optical disk is deemed one virtual disk and is rendered accessible from an existing generalized OS (operating system) as discussed in the bulletin of the Institute of Electronics, Information and Communication Engineers of Japan, "D-I, Vol. J72-D-I, No. 6, pp. 414-422". The technique, however, makes the optical disk look like as if it were rewritable many times it supposes the virtual disk being a set of virtual sectors which can be repeatedly rewritten. It is not applicable to a rewritable type optical disk.